This application claims the priorities of Korean Patent Application No. 2002-29297, filed on May 27, 2002, and Korean Patent Application No. 2002-62108 filed, on Oct. 11, 2002, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein in their entirety by reference.
1. Field of the Invention
The present invention relates to a half ball valve, and more particularly, to a half ball valve installed on a pipeline to open and close fluid flowing in the pipe.
2. Description of the Related Art
Typically, a ball valve installed on a pipeline controls the flow of fluid in the pipeline. The ball valve opens and closes a passage of fluid flowing in the pipeline by a ball rotating in a valve seat provided inside a body.
The ball valve is classified into a manual type and an electromotive type according to the type of operation. The ball valve controlling fluid flowing in the pipeline by a ball is widely used in a fan coil or heat exchanger of various air conditioners, an automatic open/close valve or protecting a control valve, protecting various fluid mechanisms or mechanical apparatuses, water supply and hot water supply, and vending machines.
A valve for a liquid pipe and a liquid tank having various sizes and structures is well known in relation to the ball valve. In most cases, for example, a gap between a ball and the inner wall of a body or a dead space where liquid remains should not be formed around the ball. If the gap is formed, fluid can enter into the gap during the opening/closing process of the valve and another fluid passing the ball valve can be contaminated by the fluid remaining in the gap or the dead space. However, it is difficult to prevent formation of the gap between the ball and the inner wall of the body or the dead space because the ball valve requires a superior assembly feature and a superior water seal maintenance feature when the fluid flow is blocked and a relatively less operation torque during the opening/closing of a passage.
Korean Utility Model Registration No. 0269119 discloses a ball which opens and closes a passage by being rotated in a pair of valve seats installed at an inlet connection hole and an outlet connection hole formed in a body by the operation of a control lever. In this case, a superior water seal maintenance feature is exhibited between the valve seat and ball. However, since a gap between the ball and the inner wall of the body or the dead space is formed, when the valve is closed, fluid is confined in a passage in the ball so that the fluid intrudes into the gap between the ball and the inner wall of the body and is deposited in the gap or the dead space.
German Patent No. 9408156 U1 discloses a half type ball valve having a packing completely covering an inner wall of a body defining a hemispherical cavity accommodating a ball having a passage formed therein coaxially with a connection hole formed in the body. The packing manufactured of polytetrafluoroethylene (PTFE) prevents deposition of fluid intruding between the ball and the inner wall of the body. However, when the packing is damaged, the entire packing set should be replaced with a new one. Furthermore, when the passage is blocked, the fluid passing through the passage in the ball is confined in the passage in the ball.
Also, Korean Utility Model Registration No. 0138535 discloses a half ball valve. The half ball valve includes a body in which a cavity, an inlet connection hole, and an outlet connection hole are formed, a hemispherical ball accommodated in the cavity of the body to be capable of rotating between open and close positions at which the inlet connection hole and the outlet connection hole are connected and disconnected, respectively, and having a passage formed therein to connect the inlet connection hole and the outlet connection hole at the open position, and a cover arranged at the lower portion of the housing to close the cavity. When the ball is positioned at the close position, a pair of seal members, each having a dome shaped lower portion to cover the inlet connection hole and the outlet connection hole, are coupled to a partial area of the outer surface of the ball, that is, the outer surface area of the ball approximately perpendicular to the axis of the passage in the ball. In the half ball valve, however, a gap is formed between the outer surface of the ball which is not coupled to the seal member and the body so that fluid intrudes into the gap when the ball is rotated to open or close the passage. Furthermore, when the passage is blocked, fluid passing through the passage in the ball is confined in the passage. The fluid confined in the passage in the ball intrudes into the gap between the outer surface of the ball and the body and is deposited therein. Also, since the seal member needs to be provided at the outer surface of the ball, the size of the ball increases.
In the above-described ball valve or half ball valve, the size of the ball is large and there is a problem that fluid flowing in the pipeline is confined in the passage of the ball when the passage of the pipeline is blocked. In the process of rotating the ball to open/close the passage, the fluid passing through the passage in the ball intrudes into the gap between the body and the inner wall of the ball or the dead space and remains and is deposited therein. Thus, when the ball is rotated through the control lever connected by a stem the opening/closing of the ball is not smooth so that a problem occurs in the operation of the ball valve. Also, since the fluid initially flowing through the pipeline remains in the gap or dead space between the body and the ball, when fluid having different physical property or color is transferred through the pipeline, the fluid having different physical property or color is mixed with the initial fluid remaining in the gap between the inner wall of the body and the ball or the dead space so that the physical property or color of the fluid transferred later is changed. Thus, in a pipeline on which the conventional ball valve is installed, when fluid having different physical property or color is to be transferred through the pipeline through which initial fluid has been transferred and the initial fluid remains in the gap between the inner wall of the body and the ball or the dead space, the ball valve installed on the pipeline needs to be inconveniently disassembled and the fluid remaining in the gap between the inner wall of the body and the ball or the dead space should be clearly removed and the ball valve is reassembled and the fluid having different physical property or color is transferred through the pipeline.